This invention is in the field of seat belt buckles for use in a variety of vehicles to secure occupants therein. A great number of seat buckles have been devised and patented for use in a variety of applications. For example, in the U.S. Pat. Nos. 3,760,467 and 3,807,000 there are disclosed push button seat belt buckles wherein a latch plate is slidably mounted in a pair of channels secured within the main buckle housing. A spring is provided on one side of the latch plate whereas a push button is provided on the opposite side of the latch plate to allow control of movement of the latch plate which engages and disengages a tongue inserted into the cavity of the buckle housing. The housing disclosed in the aforementioned patents may be cast in metal.
In order to produce a low-cost seat belt buckle, the buckle housing may be produced from plastic in lieu of metal. A problem with the prior plastic buckles is the failure of the plastic buckle housing when subjected to the various load tests that are required prior to installation of the buckle in a vehicle. In one embodiment disclosed herein, a pair of mtal reinforcing plates are positioned within the buckle housing to provide the necessary strength and to prevent the buckle from failing during load tests. The buckle is designed so as to transfer the lateral force exerted by the tongue through a movable latch plate and onto a pair of upright channels which in turn transfer the force onto the reinforcing plates fixedly secured to the plastic buckle housing. Thus, failure of the housing is prevented while simultaneously providing an attractive, low-cost buckle. Other patents of interest are the U.S. Pat. Nos. 3,911,236, which discloses a laminated buckle, and 3,807,000 which discloses a leaf spring for urging a latch plate into engagement with the buckle tongue. In another embodiment disclosed herein, one of the reinforcing plates is replaced with a plastic block having load transfer pins to transfer the tongue force from the upright channels to the buckle main body.